The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hybrid powertrains typically include a first torque generator, an internal combustion engine (ICE), for example, and a second torque generator, an electric machine (EM), for example, each of which can provide torque to a driveline to propel a vehicle. Two types of hybrid powertrains include a full hybrid powertrain and a mild hybrid powertrain. In a full hybrid powertrain, the EM can drive the drivetrain directly, without transferring torque through a component of the ICE. In a mild hybrid configuration, the EM is coupled with the ICE, through the accessory drive, for example, whereby torque generated by the EM is transferred to the drivetrain through the ICE. An exemplary mild hybrid powertrain includes a so-called belt alternator starter (BAS) system. In the BAS system, the EM is coupled to the ICE via a traditional belt and pulley configuration, which drives other accessory components including, but not limited to, pumps and compressors.
Powertrain torque control typically includes two torque control domains: axle torque and propulsion torque. In a mild hybrid powertrain, the propulsion torque is the output torque at the crankshaft of the ICE, which includes the EM torque contribution.
Powertrain systems also include several torque features, each of which seeks to influence the amount of drive torque at various points along the powertrain system. An upper level or global torque feature is a vehicle driver, who commands a desired output torque from the torque source(s) or a desired axle torque based on a driver input. Exemplary driver inputs include, but are not limited to, an accelerator pedal and a cruise control system. Modern powertrain systems include additional torque features or torque requests such as vehicle stability control systems, traction control systems, engine overspeed protection systems, transmission shift quality systems, engine and/or transmission component protection systems and/or driveline component protection systems, among several others. The torque features can number in the tens to over a hundred, depending upon the particular configuration of the powertrain system.
The torque features of a particular powertrain system are independent and can often seek to control the drive torque at the same time. Because the powertrain system can only produce a single drive torque value at any time, an arbitration system is required to determine the correct drive torque to produce. A control module is typically provided for arbitrating the multiple torque requests. In a hybrid powertrain system, this control module is responsible for arbitrating torque requests for a plurality of torque generators (e.g., the ICE and EM).